Baby Lisa's Family Mark Her First Birthday Privately

Missing Lisa Irwin turns 1 Friday, and as the investigation into her disappearance continues, her family will mark the day by reflecting in private.

"This is a very tough day for them," one of the family's attorneys, Joe Tacopina, said on Good Morning America of Lisa's parents, Deborah Bradley and Jeremy Irwin.

"This is not a day of celebration right now. Obviously, they're very hopeful. They believe that Lisa is still alive, but they're going to recognize this day and deal with this day very privately."

Lisa's Facebook page has been inundated with heart-wrenching birthday wishes, and some people have posted photos of cakes and pink donuts with sprinkles.

Missing since the pre-dawn hours of Oct. 4, Lisa disappeared from her parents' Kansas City, Mo., home sometime between when Bradley put her to bed at 6:40 p.m. and Irwin returned from work at 4 a.m.

The parents continue to have a contentious relationship with police, who they insist view them as suspects, while police maintain they have no suspects in the case.

On Thursday, Lisa's parents finally allowed her two older half-brothers to submit to a long-awaited interview with authorities. Irwin and Bradley have previously resisted claiming fear the boys, 5 and 8, would be traumatized by investigators. But police made sure the boys were interviewed by experts in working with children.

Another family attorney, John Picerno, said he was informed by an FBI agent who observed the taped interviews with the boys that they "went well," but that they yielded "no new developments."

Police are still eager to speak with Irwin and Bradley separately, but their attorneys point out the pair have already spent more than 30 hours answering questions and say any more questions authorities have can be submitted through lawyers.

"This idea that they are not cooperating is just fantasy," Picerno said. "There's nothing more to be said."